From the shell, type the command: install_pg
That's it. Alternatively, shoot an email to support.

I know already about postgresql, what does install_pg do ?

Create database directory, default to ~/pg

Install database system

Edit the postgresql.conf for the port.

Create a server start/stop scripts in ~/pg/start

Edit crontab to start server on reboots.

Starts the server.

Create a default user database.

Send an email notice to the calling user,
and saves a text copy in ~/pg/email.txt.

So basically you're up and running, ready to go.
It can take one argument: the database directory instead of "pg".
One PostGreSQL user is created, with the same name as your main account,
and no password. see below to change the password.

This install script does run a number of checks and avoid overwriting
existing data and files. In which case it will fail and stop
with an error message, and exit status 1. If all goes well,
exits status 0.

How to create PostGreSQL users ?

When PostGres is installed in your account, there is a default
user with the same name as the account (login) name.

You can create additional users with the createuser command:
createuser <new-user-name> . see man createuser
For details on options to create user from the shell, in particular the
-p and -d options.

From SQL: CREATE USER <new-user-name>. inside
psql, see \h CREATE USER for details.
This same SQL command can be used within applications and programs.

Changing PostGreSQL users password

This SQL command change a specific user's password:ALTER USER [user name] WITH PASSWORD '[new password]'
If you have not created users yet, put your main login name for [user name].

I want to install a PostGreSQL manually, on my own

No problem. the script above is just convenience.
Here are quick-steps to install your own postgresql server on your own:

issue the following command from the shell: initdb -D pg
replace "pg" with a directory of your choice.

Then edit the file pg/postgresql.conf
and change the port number to the one (NN) support@rootr.net allocated you (shot
an email to support if you don't have one already): port = NN

Also add this in your .bash_profile (or .profile): export PGPORT=NN.
If you use csh or tcsh: setenv PGPORT NN.

To start the postgresql server: pg_ctl -D pg -l pg/log start

Then create a datbase: createdb test
replace "test" with a database name of your choice.

The postgresql system is now ready, and can be
accessed with: psql test